This invention relates to an antenna, equipped with a dielectric insert, for use with a level meter that operates employing the radar principle.
A horn antenna for radar systems, its antenna cavity filled at least partly by a dielectric insert, has been described earlier, for instance, in DE 100 57 441 A1. Radar-type level meters utilizing that principle are used for measuring the level of liquids and granular materials. A microwave beam is transmitted via an antenna and is recaptured upon reflection off the surface of the medium being measured. The level of the medium can be calculated, for instance, by means of a runtime measurement.
As described in DE 100 57 441 A1, there are various applications for which the antenna of a radar-based level meter needs to be equipped with a dielectric insert. According to the description in that publication, the dielectric material is applied, for example, by being molded into the antenna interior. That publication also describes how the dielectric insert is bonded in an antenna by a baking or sintering process. That publication continues to describe the coating of the outer surface of the dielectric insert with a conductive layer as proposed, for instance, in DE 196 17 963 A1.
In practical use, however, it has been found that any such bonding is fraught with problems in that it either has a negative effect on the dielectric properties, and thus for instance on the beam characteristics of the antenna, or, depending on the type of bonding, only certain dielectric materials can be used.